I'm going to guess that you are a very new nurse, and very new to the ED.
Please discuss with your preceptor, immediately:
1. Why do we insist that those who present with suicidal or homicidal ideation remove all clothing? Hint: it's not about the patient harming him/herself with underwear - it's about what objects can be hidden in clothing that most definitely can harm the patient, you, and anyone else. And do not underestimate the usefulness of seemingly innocuous objects, including underwear, to someone who unfortunately is motivated to do harm.
2. Educational resources for you to review to familiarize yourself with common responses to trauma and stress, and the common sequelae to these destabilizing events. That you appear to have some empathy is positive, but you have an immediate need to develop better boundaries so that you can manage the situation clinically, which is your job.
3. We are all human, and yes we notice where an individual patient falls on the spectrum of features that we personally find attractive. But if you are properly focused on the clinical situation, that notice lasts for approximately 2 seconds. Dwelling on it for any longer than that ... means that your attention is not where it should be.
4. How can you better prepare for your next patient with a psychiatric complaint? What supplies should you gather at the outset - appropriate-sized gown, socks, scrub/pajama pants, urine cup for specimen, etc. - to streamline the process?